P ediatric hospital medicine (PHM) is in the midst of an exciting period of growth. In 2016, the American Board of Medical Specialties approved the petition for PHM to become the newest pediatric subspecialty, taking PHM on a divergent path from the Focused Practice in Hospital Medicine designation established for adult hospitalists. Establishment as a subspecialty has allowed PHM to defi ne the unique skills and qualifi cations that hospitalists bring to patients and the healthcare system. These skills and qualifi cations are delineated in the PHM core competencies and national fellowship curriculum. 1,2 In order to realize the vision of PHM to improve care for hospitalized children described by Roberts et al., 3 concerted efforts are needed to train and retain a workforce that is equipped with the skills to catalyze improvements in inpatient pediatric care. We discuss challenges and opportunities facing PHM in workforce development, sustainability of clinical work models, and interhospital collaboration.
FELLOWSHIP TRAINING AND THE PHM PIPELINEThe development of PHM as a subspecialty was driven by a number of factors. 4 The acuity of hospitalized children has increased signifi cantly, with a population comprised of more children with complex chronic conditions and/or technology dependence, serious complications of acute conditions, and acute mental health problems. At the same time, the medical and behavioral conditions seen by outpatient general pediatricians have become more complex and time intensive, with these practitioners less likely to work in inpatient settings. Hospitalist care has positive impacts on healthcare effi ciency and value, and both parents and primary care pediatricians report high levels of satisfaction with the healthcare delivered by PHM services. 4 A national count of the number of pediatric hospitalists is currently lacking. Conservative estimates suggest that at least 3,000 pediatric hospitalists currently practice in the United States. 5 These hospitalists have highly varied scopes of practice and work across diverse settings-more diverse, perhaps, than any other pediatric subspecialty. Although diffi cult to quantify, we estimate that approximately one-third of pediatric hospitalists in the US work in community hospitals and the remainder practice at children's hospitals. 6 Many of the needs of hospitalized children differ across these settings, and the roles and challenges faced by hospitalists in these settings correspondingly differ. Community hospitalists frequently take active roles in newborn care and emergency department consultation, often without the support of other pediatric subspecialties. 7 In contrast, hospitalists working at children's hospitals more frequently care for highly complex patients, often collaborate across multiple specialties and assume nonclinical roles in quality improvement (QI), research, and medical education.